Boot upper



FIG. 1 is a perspective view of the ornamental design for a boot upper described and shown herein.

FIG. 2 is a left side elevational view thereof.

FIG. 3 is a right side elevational view thereof.

FIG. 4 is a top view thereof.

FIG. 5 is a rear elevational view thereof; and,

FIG. 6 is a top view thereof.

The surfaces of the articles not shown in the drawing, and the portions of articles shown in phantom lines, form no part of the claimed design. 

The ornamental design for a boot upper, as shown and described. 